public class TestBinaryTree {
    static class TreeNode {
        public char val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(char val) {
            this.val = val;
        }
    }

    public TreeNode createNode() {
        TreeNode A=new TreeNode('A');
        TreeNode B=new TreeNode('B');
        TreeNode C=new TreeNode('C');
        TreeNode D=new TreeNode('D');
        TreeNode E=new TreeNode('E');
        TreeNode F=new TreeNode('F');
        TreeNode G=new TreeNode('G');
        TreeNode H=new TreeNode('H');

        A.left=B;
        A.right=C;
        B.left=D;
        B.right=E;
        C.left=F;
        C.right=G;
        E.right=H;

        return A;
    }

//    前序遍历
    void preOrder(TreeNode root) {
        if(root==null) return;
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

//    中序遍历
    void inOrder(TreeNode root) {
        if(root==null) return;
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);
    }

    //    后序遍历
    void postOrder(TreeNode root) {
        if(root==null) return;
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }

//    获取树中节点的个数
    public int size(TreeNode root) {
        if(root==null) return 0;
//        if(root.left==null && root.right==null)return 1;
        return size(root.left)+size(root.right)+1;
    }

    static int nodeSize;
    public void size2(TreeNode root) {
        if(root==null)return;
        nodeSize++;
        size2(root.left);
        size2(root.right);
    }

    /**
     * 求叶子节点的个数
     * 1.递归
     * 2.遍历
     */
    public int getLeafNodeCount(TreeNode root) {
        if(root==null) return 0;
        if(root.left==null && root.right==null) return 1;
        return getLeafNodeCount(root.left)+
                getLeafNodeCount(root.right);
    }

    static int leafNodeCount;
    public void getLeafNodeCount2(TreeNode root) {
        if(root==null) return;
        if(root.left==null && root.right==null) leafNodeCount++;
        getLeafNodeCount2(root.left);
        getLeafNodeCount2(root.right);
    }

//    判断第k层有多少个节点
    public int getKLevelNodeCount(TreeNode root,int k) {
        if(root==null)return 0;
        if(k==1) return 1;
        return getKLevelNodeCount(root.left,k-1)+
                getKLevelNodeCount(root.right,k-1);
    }

//    求树的最大高度
    public int getHeight(TreeNode root) {
        if(root==null) return 0;
        int leftHeight=getHeight(root.left);
        int rightHeight=getHeight(root.right);
        return leftHeight>rightHeight?
                leftHeight+1:
                rightHeight+1;
    }

//    找到指定值所在的节点
    public TreeNode find(TreeNode root,char val) {
        if(root==null) return null;
        if(root.val==val)return root;
        TreeNode ret=find(root.left,val);
        if(ret!=null) return ret;

        ret=find(root.right,val);
        if(ret!=null) return ret;
        return null;
    }
}
